This text is designed for a two-semester course in data structures andprogramming. For several years, we have taught a course in data structuresto students who have had a semester course in high-level language program-ming and a semester course in assembly language programming. We foundthat a considerable amount of time was spent in teaching programming tech-niques because the students had not had sufficient exposure to programmingand were unable to implement abstract structures on their own. Thebrighter students eventually caught on to what was being done. The weakerstudents never did. Based on this experience, we have reached the firm con-viction that a first course in data structures must go hand in hand with asecond course in programming. This text is a product of that conviction. The text introduces abstract concepts, shows how those concepts areuseful in problem solving and then shows how the abstractions can be madeconcrete by using a programming language. Equal emphasis is placed onboth the abstract and the concrete versions of a concept, so that the studentlearns about the concept itself, its implementation, and its application. The language used in this text is Pascal. Pascal is well-suited to such acourse since it contains the control structures necessary to make programsreadable and allows basic data structures such as stacks, linked lists, and treesto be implemented in a variety of ways. This allows the student to appre-ciate the choices and tradeoffs which face a programmer in a real situation.The only prerequisite for students using this text is a one-semester coursein programming. Students who have had a course in programming using suchlanguages as FORTRAN or PL/I can use this text together with one of theelementary Pascal texts listed in the bibliography. Chapter 1 and the Ap-pendix also provide information necessary for such students to acquaintthemselves with Pascal. Chapter 1 is an introduction to data structures. Section 1.1 introducesthe concept of an abstract data structure and the concept of an implementa-tion. Sections 1.2 and 1.3 introduce arrays and records in Pascal. Theimplementations of these two data structures as well as their applicationsare covered.X